The present invention relates to a control apparatus for the internal combustion engine which can establish an optimum combustion by detecting the combustion pressure in the cylinder and controlling the exhaust gas reflux rate, the ignition timing and the fuel injection timing or the fuel injection rate for the intake stroke in order to increase the fuel economy and reduce the release of the regulated components in the exhaust gas.
The statutory regulations regarding fuel consumption and exhaust gasses have been increased in severity in all countries every year. Controlling the ignition timing and the fuel injection amount in response to the actual operational status by microcomputers is commonly used.
In order to optimize the torque and the fuel consumption rate in port-injection type engines, it is known to the skilled in the art that the ignition timing is optimally adjusted so that the angle of the crankshaft for providing the maximum in-cylinder pressure may be at 12 degrees after top dead center (which is disclosed in the article, xe2x80x9cOptimal Ignition Timing Feedback Control Method in Spark Ignition Enginexe2x80x9d, by Fujii and Kawai, et. al. in Preprint Paper Pp. 954, Automotive Engineering Society conference, 1995.) (Hereinafter referred to as xe2x80x9cPrior Art 1xe2x80x9d)
Japanese Patent Application Laid-Open No. 3-233262 (1991) discloses a technology in which the heat efficiency is obtained from the output from the in-cylinder pressure sensor and the engine is operated at the region in which the efficiency of the engine is maintained to be large enough by controlling the EGR rate, the ignition timing and the fuel supply rate. (Hereinafter referred to as xe2x80x9cPrior Art 211)
In addition, Japanese Patent Application Laid-Open No. 3-246352 (1991) discloses a technology in which the combustion status such as flameout is detected with a high degree of accuracy by estimating the equivalent workload from the heat release amount and the peak position based on the output from the in-cylinder pressure sensor (Hereinafter referred to as xe2x80x9cPrior Art 3xe2x80x9d)
However, the technology disclosed in Prior Art 1 aims to control the peak position of the in-cylinder pressure, the technology disclosed in Prior Art 2 is based on the heat efficiency of the engine, that is, the relation between the heat generation rate and the heat loss rate, and the technology disclosed in Prior Art 3 aims to obtain the average workload at the combustion stroke from the heat generation amount. Thus, those technologies do not consider explicitly the heat generation rate itself translating the waveform pattern indicating the combustion status. Though it is important to operate the heat generation rate with respect to the crank angle, that is, the pulse width and its peak height of the waveform of the combustion pattern in order to control the combustion (burn) time having a great impact on the engine performance, the prior art described above aim to operate those parameters indirectly, and there remains such a problem that an optimal control can not be always attained.
The present invention aims to solve the problems in the above described prior art which provides a method for shaping directly the waveform pattern of the heat generation rate. Thus, it will be appreciated that optimal combustion control can be established with less computational complexity by correlating explicitly the manipulated variables and the pattern reshaping, and by controlling the width of the waveform and its peak level independently.
In either case that there is afterburning in which the burning rate after ignition is slow as shown in FIG. 2(A), the combustion time is short and the peak level of the heat generation is higher as shown in FIG. 2(B) or that there are two or more peaks in the heat generation rate, the heat efficiency decreases and the fuel consumption increases. Thus, gaseous NOx and HC emission as the regulated components increases.
Another object of the present invention is to provide a combustion control device for an internal combustion engine enabling an improvement of the combustion status with less computational complexity based on the heat generation rate of the individual cylinders in service and optimizing the fuel economy and the gaseous emission.
The above object can be achieved by a combustion control device having an in-cylinder pressure detector for detecting the in-cylinder pressure in connection with the combustion in the engine; apparatus for estimating the heat generation rate with respect to the angle of the crank shaft of the cylinder according to the output from said in-cylinder pressure detector; and a controller for controlling a value related to at least either of the ignition timing, the fuel injection timing, the fuel injection ratio for the intake stroke, the in-cylinder gas flow control variable, the EGR control variable, the intake valve timing control variable or the exhaust valve timing control variable so that the in-cylinder combustion state pattern obtained by the heat generation rate estimation apparatus may be reshaped into a predefined waveform pattern.